mach3 close loop system can be made by contract from the liner scale and then make comparisons to the position.
Order to match or not. If not add value to the mach3 is calculated to order for another or not.

 
 Thank you

Mach is open loop and the only closing of the loop that you will get is if you use servo motors, the loop will then be closed between motors and drives but it will not be closed back to Mach.
Hood